Sturgeons are an interesting and unique species of fish known for their economic value and biological significance. With regard to its unique physiological requirements, relatively shorter period required for sexual maturity and higher resistance to stress as compared to other species, the culture of A. stellatus has received a lot of attention in the recent years. However a long term commitment to an integrated approach to achieve the biotechnique of brood stock production can be beneficial for the development of sturgeon aquaculture.
Successful recovery of sturgeon stocks is dependent on many factors including investigations on the functioning of their reproduction system and factors responsible for the improvement and development of gonads. However the peculiarities of sturgeon gonads and their prolonged sexual maturity were obstacles while investigating trends in gonad development. Under natural conditions, female A. stellatus begin to reproduce at an age of 8 to 17 years, while the equivalent age in males is 5 to 13 years. Factors affecting reproduction and growth in fishing including sturgeons can be divided into categories; internal factors and external factors. Among the internal factors, genetic and physiological factors and all processes related to endocrine glands are considered to be important, while a wide array of ecological factors including light, temperature, pH, feeding and certain physical and chemical characteristics of water are considered as critical external factors affecting reproduction. Diet composition is one of the most important deterministic external factors that affect gonadal development in fish.
Highly unsaturated fatty acids (HUFA) with 20 or more carbon atoms affect, directly or through their metabolites, fish maturation and steroidogenesis. In some species, HUFA in broodstock diets increases fecundity, fertilization and egg quality. As in higher vertebrates, vitamin E deficiency affects reproductive performance, causing immature gonads and lower hatching rate and survival of offspring. HUFA deficiency in diets led to delay in vitellogenesis in rainbow trout (Oncorhynchus mykiss). On the other hand HUFAs also play an important role in regulating the synthesis of ecosanoids and prostaglandins, a large group of highly bioactive hormones that stimulate the production of steroids, gonad development and ovulation. Fish farmed on diets containing HUFA have been known to show increased fertilization rates and fecundity as well as increase in quality and survival of eggs and hatching rates. Apart from HUFA, vitamin C (ascorbic acid) and E (α tocopherol) are important because of their powerful antioxidant properties during different stages of development of reproduction system in fish.
Vitamin E is a fat soluble vitamin which acts as an antioxidant essential for reproduction in vertebrates. Deficiencies in Vitamin E leads to delay in development of gonads, decrease in hatching rates and lowering survival rate of larvae. Natural antioxidants, including vitamin E, and C play important roles in reproduction by maintaining antioxidant protection of the spermatozoa during spermatogenesis and affects their motility, membrane fluidity and fertility.
Vitamins C and E neutralizes unstable free radicals that are produced during the production of other steroid hormones. The antioxidant function of vitamins C and E can provide an important protective role for the sperm cells during spermatogenesis and until fertilization by reducing the risk of lipid peroxidation, which is detrimental for sperm motility. Ascorbic acid has been shown to play an important role in salmonid reproduction and its role in steroidogenesis and vitellogenesis has been reported. The role of vitamin E has also been documented in gonadal development and fertilization rate in carps.
The role of vitamin C in the functioning of the reproduction system in salmonidae has been studied. Vitamin C is also critical in the survival and development of larvae and it is also effective in the formation of collagen, during embryonic development.
Phytoestrogens a diverse group of naturally occurring non steroidal plant compounds found in soybean extract are known to affect vitellogenesis and advance oocyte maturation. Genistein, an estrogenic isoflavone compound on the endocrine process of gametogenesis and on reproduction efficiency of the rainbow trout Oncorhynchus mykiss has been studied. The effects of genistein and equol on the gonadal development of Japanese Medaks (Oryzia latipes) have been documented.
The gonadal structure in different sturgeon species is dependant on the different stages of growth. Therefore the stage of gametogenesis may be used as index for all sturgeon species. Several papers have demonstrated that certain blood parameters can be used as indicators of the physiological condition of the fish during the selection of brood stock. With regard to the significance of artificial breeding programs of farmed A. stellatus to develop sturgeon aquaculture in the country, the investigation of blood parameters has been considered an important aspect of this study. Hematological studies give us an insight of gonadal growth and development of these species under farmed conditions and thus can be valuable in the conservation of these valuable stocks.
Considering that sexual maturity in sturgeons is reached very late an improvement in broodstock nutrition and feeding can greatly improve egg and sperm quality.
The main objective of this study is to investigate the effects of diets containing soybean and vitamins C and E in the advancement or induction of sexual maturity in farmed A. stellatus and to develop a relationship between dietary nutrients that affect gonadal development and fecundity in this species and other factors such as sex, farming conditions, and ecological factors. To accomplish this, the relationship between blood parameters, osmosis and sex hormones in male and female farmed A. stellatus during different stages of sexual maturity and different seasons was studied and effective indices to differentiate spawners were developed. In this way the biotechnique of brood stock production and artificial breeding and rearing of farmed sturgeons, particularly A. stellatus was developed for the first time in Iran. This will no doubt revolutionize the aquaculture industry in the country.
The operating stages of this project were carried out in three phases:                1. Brood stock production through control of physical-chemical parameters in water and using different diets in both sexes (males and females)        2. Study of histological and hematological parameters and osmosis of ions and hormones        3. Artificial breeding, harvesting of eggs and sperm and caviar and offspring        4. production using GnRH protocol        